Grok 4.3 vs Mercury 3
Mercury 3 costs 7.1x less per output token than Grok 4.3 ($0.35 vs $2.50 per million). Updated October 21, 2026; 5 benchmarks have a result for both.
Grok 4.3 or Mercury 3: which to pick
Only Grok 4.3 has a coding score, 37.4 on the Vibe Coding Index; Mercury 3 has none, so the two cannot be ranked on coding.
Pick Mercury 3 for output tokens 7.1x cheaper ($0.35 vs $2.50 per million) and work measured by Design Arena: websites or Design Arena: UI components, where it leads.
- Shared results
- 5
- Grok 4.3 only
- 99
- Mercury 3 only
- 0
- Like-for-like categories
- 1 of 9
Only benchmarks that tested both models count toward a pick; a result only one model has is shown but not compared.
Which one for your work
Each card is decided by one number both models carry. Where only one has it, the card says so and makes no call.
Coding
Vibe Coding Index, six public coding benchmarks
No call
Only Grok 4.3 has a coding score, so no call is made.
One side not measured
Intelligence
AA Intelligence Index
No call
Only Grok 4.3 has a AA Intelligence Index result, 24.9.
Directional only
Agentic work
AA Agentic Index
No call
Only Grok 4.3 has a AA Agentic Index result, 15.5.
Directional only
Reasoning
GPQA Diamond
No call
Only Grok 4.3 has a GPQA Diamond result, 91.4%.
Directional only
Knowledge
MMLU Pro
No call
Only Grok 4.3 has a MMLU Pro result, 85.8%.
Directional only
Web design
Design Arena: websites
Mercury 3
Mercury 3 leads, 1244 against 1196.
Same board, both measured
Long documents
Listed context window
No call
Both take 1M tokens.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Mercury 3
Grok 4.3 $0.0025, Mercury 3 $0.0003 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
No call
Only Grok 4.3 has the number, $0.31.
Directional only
At a glance
- Coding index
- Grok 4.3 37.4 from 3 benchmarks, Mercury 3 not benchmarked.
- Widest category
- Web design, 6.5 points apart on average over 5 shared benchmarks.
- Widest single gap
- Design Arena: UI components: Grok 4.3 1192 against Mercury 3 1270, 9.8 points apart on a 0 to 100 scale.
- Output price
- Grok 4.3 $2.50 against Mercury 3 $0.35 per million output tokens, 7.1x apart.
- Context window
- Both take 1M tokens.
Benchmark by benchmark
First the score: boards each model leads, per category, where both have a result. Then every board, a category to a fold; bars are each result on a 0 to 100 scale, so compare the two in a row, not one row with another.
| Category | Grok 4.3 | Bars | Mercury 3 | Ties |
|---|---|---|---|---|
| Web design | 0 | 5 | ||
| All shared boards | 0 | 5 |
CodingDirectional onlySix of these boards feed the Vibe Coding Index18 boards, none shared
| Benchmark | Grok 4.3 | Mercury 3 | Leader |
|---|---|---|---|
| LMArena WebDev | 1358 | Not measured | Only Grok 4.3 measured |
| AA Coding Index | 42.2 | Not measured | Only Grok 4.3 measured |
| LiveCodeBench (Vals AI) | 84.5% | Not measured | Only Grok 4.3 measured |
| SWE-bench Verified (Vals AI) | 71.4% | Not measured | Only Grok 4.3 measured |
| Vibe Code Bench (Vals AI) | 19.4% | Not measured | Only Grok 4.3 measured |
| Code migration (Vals AI) | 6.8% | Not measured | Only Grok 4.3 measured |
| ProgramBench (Vals AI) | 0.0% | Not measured | Only Grok 4.3 measured |
| Terminal-Bench 2.1 (Vals AI) | 42.0% | Not measured | Only Grok 4.3 measured |
| SkillsBench (Vals AI) | 40.6% | Not measured | Only Grok 4.3 measured |
| SciCode | 48.3% | Not measured | Only Grok 4.3 measured |
| Terminal-Bench Hard (Artificial Analysis run) | 37.9% | Not measured | Only Grok 4.3 measured |
| WeirdML | 49.9% | Not measured | Only Grok 4.3 measured |
| ALE-Bench | 944.2 | Not measured | Only Grok 4.3 measured |
| LMArena Text: coding | 1415 | Not measured | Only Grok 4.3 measured |
| LMArena Text: software and IT | 1416 | Not measured | Only Grok 4.3 measured |
| LMArena WebDev: React | 1353 | Not measured | Only Grok 4.3 measured |
| LMArena WebDev: HTML | 1367 | Not measured | Only Grok 4.3 measured |
| LMArena WebDev: from an image | 1375 | Not measured | Only Grok 4.3 measured |
| Neither model has a result on the other 21 boards here | |||
IntelligenceDirectional onlyPublic boards, shown as published, kept out of the index1 board, none shared
| Benchmark | Grok 4.3 | Mercury 3 | Leader |
|---|---|---|---|
| AA Intelligence Index | 24.9 | Not measured | Only Grok 4.3 measured |
| Neither model has a result on the other 1 board here | |||
Agentic workDirectional onlyPublic boards, shown as published, kept out of the index16 boards, none shared
| Benchmark | Grok 4.3 | Mercury 3 | Leader |
|---|---|---|---|
| AA Agentic Index | 15.5 | Not measured | Only Grok 4.3 measured |
| Design Arena: agents building web apps | 1126 | Not measured | Only Grok 4.3 measured |
| Design Arena: agents building full-stack apps | 1006 | Not measured | Only Grok 4.3 measured |
| Design Arena: agents building mobile apps | 1059 | Not measured | Only Grok 4.3 measured |
| Design Arena: agents building Android apps | 961 | Not measured | Only Grok 4.3 measured |
| Design Arena: agents building Godot games | 914 | Not measured | Only Grok 4.3 measured |
| Design Arena: agents building games | 1007 | Not measured | Only Grok 4.3 measured |
| Design Arena: HTML slides | 1008 | Not measured | Only Grok 4.3 measured |
| Design Arena: PowerPoint slides | 1013 | Not measured | Only Grok 4.3 measured |
| Finance Agent (Vals AI) | 37.7% | Not measured | Only Grok 4.3 measured |
| Tax Agent Bench (Vals AI) | 6.2% | Not measured | Only Grok 4.3 measured |
| Legal Research Bench (Vals AI) | 15.4% | Not measured | Only Grok 4.3 measured |
| Excel Modeling Benchmark (Vals AI) | 18.4% | Not measured | Only Grok 4.3 measured |
| τ²-Bench Telecom | 97.7% | Not measured | Only Grok 4.3 measured |
| Vending-Bench 2 | $35 | Not measured | Only Grok 4.3 measured |
| LMArena Search | 1166 | Not measured | Only Grok 4.3 measured |
| Neither model has a result on the other 25 boards here | |||
ReasoningDirectional onlyPublic boards, shown as published, kept out of the index11 boards, none shared
| Benchmark | Grok 4.3 | Mercury 3 | Leader |
|---|---|---|---|
| GPQA Diamond | 91.4% | Not measured | Only Grok 4.3 measured |
| MMMU Pro (Vals AI) | 83.1% | Not measured | Only Grok 4.3 measured |
| GPQA Diamond (Artificial Analysis run) | 90.1% | Not measured | Only Grok 4.3 measured |
| Humanity's Last Exam (Artificial Analysis run) | 37.2% | Not measured | Only Grok 4.3 measured |
| GPQA Diamond (Epoch AI run) | 88.8% | Not measured | Only Grok 4.3 measured |
| Chess puzzles | 18.0% | Not measured | Only Grok 4.3 measured |
| LMArena Text: hard prompts | 1396 | Not measured | Only Grok 4.3 measured |
| LMArena Text: expert | 1384 | Not measured | Only Grok 4.3 measured |
| LMArena Text: hard prompts in English | 1402 | Not measured | Only Grok 4.3 measured |
| LMArena Vision: diagrams | 1241 | Not measured | Only Grok 4.3 measured |
| LMArena Vision: homework | 1241 | Not measured | Only Grok 4.3 measured |
| Neither model has a result on the other 11 boards here | |||
MathDirectional onlyPublic boards, shown as published, kept out of the index6 boards, none shared
| Benchmark | Grok 4.3 | Mercury 3 | Leader |
|---|---|---|---|
| OTIS Mock AIME | 93.3% | Not measured | Only Grok 4.3 measured |
| FrontierMath, tiers 1 to 3 | 42.8% | Not measured | Only Grok 4.3 measured |
| FrontierMath, tier 4 | 14.6% | Not measured | Only Grok 4.3 measured |
| ProofBench | 11.0% | Not measured | Only Grok 4.3 measured |
| LMArena Text: math | 1387 | Not measured | Only Grok 4.3 measured |
| LMArena Text: mathematical work | 1396 | Not measured | Only Grok 4.3 measured |
| Neither model has a result on the other 7 boards here | |||
KnowledgeDirectional onlyPublic boards, shown as published, kept out of the index12 boards, none shared
| Benchmark | Grok 4.3 | Mercury 3 | Leader |
|---|---|---|---|
| MMLU Pro | 85.8% | Not measured | Only Grok 4.3 measured |
| LegalBench (Vals AI) | 84.5% | Not measured | Only Grok 4.3 measured |
| CaseLaw (Vals AI) | 79.3% | Not measured | Only Grok 4.3 measured |
| CorpFin (Vals AI) | 68.5% | Not measured | Only Grok 4.3 measured |
| TaxEval (Vals AI) | 70.8% | Not measured | Only Grok 4.3 measured |
| MortgageTax (Vals AI) | 48.3% | Not measured | Only Grok 4.3 measured |
| MedCode (Vals AI) | 38.1% | Not measured | Only Grok 4.3 measured |
| SimpleQA Verified | 33.2% | Not measured | Only Grok 4.3 measured |
| LMArena Text: science | 1399 | Not measured | Only Grok 4.3 measured |
| LMArena Text: medicine and healthcare | 1384 | Not measured | Only Grok 4.3 measured |
| LMArena Text: legal and government | 1386 | Not measured | Only Grok 4.3 measured |
| LMArena Text: business and finance | 1381 | Not measured | Only Grok 4.3 measured |
| Neither model has a result on the other 6 boards here | |||
Web designLike-for-likePublic boards, shown as published, kept out of the index05
| Benchmark | Grok 4.3 | Mercury 3 | Leader |
|---|---|---|---|
| Design Arena: websites | 1196 | 1244 | Mercury 3 |
| Design Arena: UI components | 1192 | 1270 | Mercury 3 |
| Design Arena: game dev | 1174 | 1227 | Mercury 3 |
| Design Arena: data viz | 1179 | 1207 | Mercury 3 |
| Design Arena: 3D | 1125 | Not measured | Only Grok 4.3 measured |
| Design Arena: all code categories | 1187 | 1240 | Mercury 3 |
| Design Arena: SVG | 1081 | Not measured | Only Grok 4.3 measured |
| Design Arena: ASCII art | 1125 | Not measured | Only Grok 4.3 measured |
| Neither model has a result on the other 1 board here | |||
GeneralDirectional onlyPublic boards, shown as published, kept out of the index32 boards, none shared
| Benchmark | Grok 4.3 | Mercury 3 | Leader |
|---|---|---|---|
| Public Benefits Bench (Vals AI) | 51.7% | Not measured | Only Grok 4.3 measured |
| SAGE (Vals AI) | 19.7% | Not measured | Only Grok 4.3 measured |
| MedScribe (Vals AI) | 74.4% | Not measured | Only Grok 4.3 measured |
| Vals Multimodal Index | 43.3% | Not measured | Only Grok 4.3 measured |
| IFBench | 83.3% | Not measured | Only Grok 4.3 measured |
| Long context reasoning (AA-LCR) | 75.0% | Not measured | Only Grok 4.3 measured |
| DTBench | 90.7% | Not measured | Only Grok 4.3 measured |
| LMCA | 38.3% | Not measured | Only Grok 4.3 measured |
| LMArena Text | 1397 | Not measured | Only Grok 4.3 measured |
| LMArena Text: instruction following | 1366 | Not measured | Only Grok 4.3 measured |
| LMArena Text: creative writing | 1380 | Not measured | Only Grok 4.3 measured |
| LMArena Vision | 1229 | Not measured | Only Grok 4.3 measured |
| LMArena Text: English | 1404 | Not measured | Only Grok 4.3 measured |
| LMArena Text: non-English | 1385 | Not measured | Only Grok 4.3 measured |
| LMArena Text: Chinese | 1422 | Not measured | Only Grok 4.3 measured |
| LMArena Text: German | 1395 | Not measured | Only Grok 4.3 measured |
| LMArena Text: Japanese | 1379 | Not measured | Only Grok 4.3 measured |
| LMArena Text: Korean | 1354 | Not measured | Only Grok 4.3 measured |
| LMArena Text: French | 1411 | Not measured | Only Grok 4.3 measured |
| LMArena Text: Spanish | 1399 | Not measured | Only Grok 4.3 measured |
| LMArena Text: Russian | 1399 | Not measured | Only Grok 4.3 measured |
| LMArena Text: Polish | 1398 | Not measured | Only Grok 4.3 measured |
| LMArena Text: multi-turn | 1406 | Not measured | Only Grok 4.3 measured |
| LMArena Text: longer queries | 1393 | Not measured | Only Grok 4.3 measured |
| LMArena Text: writing and language | 1385 | Not measured | Only Grok 4.3 measured |
| LMArena Text: entertainment and media | 1370 | Not measured | Only Grok 4.3 measured |
| LMArena Vision: English | 1235 | Not measured | Only Grok 4.3 measured |
| LMArena Vision: Chinese | 1257 | Not measured | Only Grok 4.3 measured |
| LMArena Vision: reading text | 1235 | Not measured | Only Grok 4.3 measured |
| LMArena Vision: humor | 1222 | Not measured | Only Grok 4.3 measured |
| LMArena Vision: recognizing things | 1217 | Not measured | Only Grok 4.3 measured |
| LMArena Vision: creative writing | 1237 | Not measured | Only Grok 4.3 measured |
| Neither model has a result on the other 14 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Grok 4.3 | Mercury 3 | Leader |
|---|---|---|---|
| Neither model has a result on 5 boards here | |||
What each workload costs
Three fixed token mixes at each model's listed price, so per-token rates become a bill.
Chat turn
1K input + 500 output tokens
Mercury 3 costs less
Repository review
50K input + 3K output tokens
Mercury 3 costs less
Agent loop
200K input + 10K output tokens
Mercury 3 costs less
Listed OpenRouter rates, without cache or batch discounts. A workload that does not fit a model's context window would need splitting.
Specification differences
The leading value in a row is marked; a row with a missing value names no leader. Our two rows are marked in red.
| Specification | SpaceXAI Grok 4.3 | Inception Mercury 3 |
|---|---|---|
| Maker | xAI | Inception |
| Weights | No public weights listed | No public weights listed |
| Released | April 30, 2026 | October 16, 2026 |
| Context window | 1M | 1M |
| Input $/Mtok | $1.25 | $0.10 |
| Output $/Mtok | $2.50 | $0.35 |
| Coding index | 37.4 | Not benchmarked |
| Independent measurements behind it | 3 | 0 |
| Cost per solved task | $0.31 | Not computable |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Grok 4.3 better than Mercury 3 for coding?
Only Grok 4.3 has a coding score, 37.4 on the Vibe Coding Index; Mercury 3 has none, so the two cannot be ranked on coding. Pick Mercury 3 for output tokens 7.1x cheaper ($0.35 vs $2.50 per million) and work measured by Design Arena: websites or Design Arena: UI components, where it leads.
Which is cheaper, Grok 4.3 or Mercury 3?
Grok 4.3 costs $1.25 per million input tokens and $2.50 per million output tokens; Mercury 3 costs $0.10 and $0.35. Cost per solved task is known for Grok 4.3 only.
Which has the bigger context window, Grok 4.3 or Mercury 3?
Neither: both take 1M tokens.
How many benchmarks is the Grok 4.3 vs Mercury 3 comparison based on?
5 benchmarks have a result for both models as of October 21, 2026. Grok 4.3's coding index rests on 3 independent benchmarks and Mercury 3's on 0. Where only one model has a result, the page says so instead of naming a winner.